The crew of a Ukrainian jetliner that crashed in Iran, killing 176 people, never made a radio call for help and were trying to turn back for the airport when their burning plane went down, an initial Iranian report said on Thursday.
Ukraine, meanwhile, said it considered a missile strike or terrorism as possible theories for the crash, despite Iran's denials.
The Iranian report suggests a sudden emergency struck the Boeing 737 operated by Ukrainian International Airlines early Wednesday morning, when it crashed, just minutes after taking off from Imam Khomeini International Airport in Tehran.
Investigators from Iran's Civil Aviation Organisation offered no immediate explanation for the disaster.
Iranian officials initially blamed a technical malfunction for the crash, something initially backed by Ukrainian officials before they said they wouldn't speculate amid an ongoing investigation.
The crash came just a few hours after Iran launched a ballistic missile attack against Iraqi military bases housing US troops amid a confrontation with Washington over it killing an Iranian Revolutionary Guard general in a drone strike last week.
More From This Section
The Ukrainian International Airlines took off at 6:12 am on Wednesday, after nearly an hour's delay at Tehran's Imam Khomeini Airport, the main airport for travellers in Iran. It gained altitude heading west, reaching nearly 8,000 feet, according to both the report and flight-tracking data.
Then something went wrong, though "no radio messages were received from the pilot regarding unusual situations", the report said. In emergencies, pilots typically immediately contact air-traffic controllers.
Eyewitnesses, including the crew of another flight passing above it, described seeing the plane engulfed in flames before crashing at 6:18 am.
The crash caused a massive explosion when the plane hit the ground, likely because the aircraft had been fully loaded with fuel for the flight to Keiv.
The report also confirmed that both of the so-called "black boxes" that contain data and cockpit communications from the plane had been recovered, though they sustained damage and some parts of their memory was lost.
It also said investigators have initially ruled out laser or electromagnetic interference as causing the crash.
Oleksiy Danilov, secretary of Ukraine's Security Council, told Ukrainian media that officials had several working theories regarding the crash, including a missile strike.
"A strike by a missile, possibly a Tor missile system, is among the main (theories), as information has surfaced on the internet about elements of a missile being found near the site of the crash," Danilov said. He did not elaborate on where he saw the information on the internet.
Ukrainian investigators that arrived in Iran earlier on Thursday currently await permission from Iranian authorities to examine the crash site and look for missile fragments, Danilov said.
The Tor is a Russian-made missile system. Russia delivered 29 Tor-M1s to Iran in 2007 as part of a USD 700 million contract. Iran has displayed the missiles in military parades as well.
Iran did not immediately respond to the Ukrainian comments. However, General Abolfazl Shekarchi, the spokesman of the Iranian armed forces, denied a missile hit the airplane in a comments reported Wednesday by the semiofficial Fars news agency. He dismissed the allegation as "psychological warfare" by foreign-based Iranian opposition groups.
Danilov also said other possible causes under consideration included a drone or another flying object crashing into the plane, a terrorist attack or an engine malfunction causing an explosion.
The plane was carrying 167 passengers and nine crew members from several countries, including 82 Iranians, at least 63 Canadians and 11 Ukrainians, according to officials. The crash just before dawn scattered flaming debris and passengers' belongings across a wide stretch of farmland.
Many of the passengers were believed to be international students attending universities in Canada; they were making their way back to Toronto by way of Keiv after visiting with family during the winter break.
Ukrainian President Volodymyr Zelenskiy said he planned to call Iranian President Hassan Rouhani about the crash and the investigation.
"Undoubtedly, the priority for Ukraine is to identify the causes of the plane crash," Zelenskiy said. "We will surely find out the truth."